It is the first confirmation of his whereabouts since Wednesday, when he fled rebel forces in the city of Aden.

The officials say he will go to Egypt for an Arab league summit on Saturday.

The Saudi authorities began air strikes in Yemen on Wednesday night, a step Iran called "dangerous".

During the second night of raids warplanes again targeted rebel positions in Yemen's capital Sanaa and an air base near the southern port city of Aden.

Reports say there were civilian casualties.

Clashes were also reported in Aden between troops loyal to President Hadi and the rebels.

Saudi Arabia says it is "defending the legitimate government" of Mr Hadi.

Legitimacy

Mr Hadi took refuge in Aden last month after fleeing Sanaa, where he had been under house arrest since the Houthis took full control of the capital in January.

On Thursday, a Saudi official said he had travelled to Riyadh, but would attend the two-day Arab summit in Egypt as the "legitimate" Yemeni president.

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Houthi rebels protested against the air strikes on Thursday

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The damage caused by the Saudi-led coalition air strikes in Sanaa was clear to see on Thursday morning

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There have been clashes between rebel fighters and militiamen loyal to President Hadi in Aden

The Saudi ambassador to the US, Adel al-Jubair, said the first wave of airstrikes over targets in Yemen "went extremely well and with no collateral damage".

He said this was "just the beginning of the campaign" which would carry on until "wisdom prevails" among the Houthi rebels.

Sources say the kingdom would consider sending troops to protect the government if it were to re-assemble in Aden in the future.

Reports said Saudi Arabia was using 100 warplanes in the operation, and its allies would contribute dozens more.

Saudi-owned Al-Arabiya TV reported that the UAE, Bahrain, Kuwait, Qatar, Jordan, Morocco and Sudan were sending aircraft, while Egypt, Jordan, Sudan and Pakistan were ready to take part in any ground offensive targeting the Houthis.

The US said it was providing "logistical and intelligence support".

However, a Houthi official warned the coalition that it risked provoking a wider war.

At the scene: BBC reporter near Sanaa

Following the air strikes, people rushed to the military sites which had been targeted to check the level of destruction.

Dozens of families meanwhile have fled Sanaa to safe places outside the city, fearing new air strikes.

There are long queues of cars at petrol stations amid fears of fuel shortages, and many shops and firms have shut. School and university classes in Sanaa have been suspended for the time being.

Some Sanaa residents see the air strikes as a way of ending the crisis, which they blame on the Houthis for taking over their city.

However angry Houthi followers and supporters of the former president, Ali Abdallah Saleh, called for protests against the attacks.

On social media, Houthi supporters have been urging them to keep advancing to the border and storm Saudi Arabia, and to blockade the strategic Bab al-Mandab Strait in the Red Sea.

Shia power Iran, which Sunni-ruled Saudi Arabia accuses of backing the rebels, also demanded an immediate halt to the strikes, which it said violated Yemen's sovereignty.

But Turkey has accused Iran of trying to dominate the region.

President Recep Tayyip Erdogan said he supported the operation against the Houthis, adding Iran's stance had begun "annoying us, Saudi Arabia and the Gulf countries".

"This is really not tolerable and Iran has to see this," he said.

A conflict that pulls in regional powers could disrupt global oil supplies, and the price of Brent crude rose almost 6% after the strikes began.

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Militiamen loyal to President Hadi have been unable to stop the Houthi advance

Media reports said at least 13 civilians were killed in Sanaa during the first day of the air strikes, and 18 people were killed in clashes between rebel fighters and soldiers and militiamen loyal to Mr Hadi in southern Yemen.

Yemeni Foreign Minister Riad Yassin told the Saudi TV channel al-Hadath that the air strikes were welcome, adding: "I hope the Houthis listen to the sound of reason. With what is happening, they forced us into this."

The Houthis have said their aim is to replace Mr Hadi's government, which they accuse of being corrupt, and to implement the outcomes of the National Dialogue that was convened when Mr Saleh was forced to hand over power in 2011 following mass protests.